Interpenetrating polymer network hydrophilic hydrogels for contact lens

ABSTRACT

An interpenetrating polymer network (IPN) composition and a process for the manufacture of hydrogel contact lens using the invention material. The polymeric materials are formed by polymerization of: (1) an unsaturated alkyl(meth)acrylate or its derivatives such as 2-hydroxyethyl methacrylate as the principle monomer; (2) optionally vinyl containing comonomer(s) to enhance the resulting hydrogel water absorbing capability; (3) polymerizable multi-functional crosslinking agent(s); (4) an irradiation initiator and/or thermal initiator; (5) optionally other additives to impart the resulting hydrogel specific properties such as ultra-violet blocking ability and handling colors; in the presence of a soluble, hydrophilic IPN agent such as polyvinylpyrrolidone (PVP) or poly-2-ethyl-2-oxazoline (PEOX) with a specific molecular weight range. The novel hydrophilic hydrogel material in the present invention can be used to produce a spherical contact lens, a toric contact lens, a multifocal contact lens, a toric-multifocal contact lens, and other medical devices. The inventive hydrogel material shows a low degree of surface friction, a low dehydration rate, and a high degree of biodeposit resistance.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of International ApplicationPCT/US99/15532, with an international filing date of Jul. 8, 1999, whichclaims the benefit of the filing of U.S. Provisional Patent ApplicationSer. No. 60/092,100, entitled IPN Hydrophilic Non-Ionic Hydrogels, filedon Jul. 8, 1998, and the specification thereof is incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention (Technical Field)

[0003] The present invention relates to an interpenetrating polymernetwork (IPN) composition, especially a hydrophilic hydrogel compositionfor contact lens. More particularly, the present invention relates topolymerization of monomers in the presence of water soluble polymers asthe IPN agents miscible with the monomer mixture using conventionalcrosslinkers or polymeric crosslinkers under ultraviolet and/Dr thermalcuring condition.

[0004] 2. Background Art

[0005] Interpenetrating polymer network (IPN) technology has beenundergoing development over the past several decades. An IPN consists ofat least two types of polymers wherein one polymer is synthesized in thepresence of an already existing polymer, or both polymers aresynthesized simultaneously.

[0006] From a chemical point of view, an IPN is a whole unit structureformed from at least two distinct polymers. An IPN thereby has thephysical and chemical properties of the constituent polymers, and thuscombines the advantages of the polymers.

[0007] Hydrophilic hydrogels prepared by an IPN process have gained agreat deal of attention in a variety of fields. The following patentsdisclose IPN hydrogels. U.S. Pat. No. 4,575,539 entitled “Drug deliverysystems including novel interpenetrating polymer networks and method,”to DeCrosta, et al., issued Mar. 11, 1986, discloses an IPN employinghydrogel beads which is formed by swelling hydrogel beads with anacrylic type swelling agent and reacting the swelling agent with acrosslinking agent such as ethyleneglycol dimethacrylate. The system soproduced has superior drug leading capacity and controlled releasecharacteristics. U.S. Pat. No. 5,644,049, entitled “Biomaterialcomprising hyaluronic acid and derivatives thereof in interpenetratingpolymer networks (IPN),” to Giusti, et al., issued Jul. 1, 1997,discloses the use of hyaluronic acid and its derivatives in IPN to forma hydrogel. The IPN biomaterial so prepared is useful in manyapplications including dermatology, microsurgery, urology, andcardiovascular systems.

[0008] In the contact lens field, hydrogels are often formed bycopolymerization of monomers with the appropriate crosslinkers. Thefollowing patents disclose hydrogels formed by copolymerization. U.S.Pat. No. 5,665,840, entitled “Polymeric Networks from Water-SolublePrepolymers,” to Pöhlmann et al., issued Sep. 9, 1997, discloses awater-soluble, crosslinkable prepolymer having monomeric structuralunits of a vinyl lactam, vinyl alcohol, alkanecarboxylic acid vinylester, vinylic crosslinking agent, and a vinylic photo initiator. Thepatent further discloses water-soluble crosslinkable prepolymer having acopolymer chain comprising 5 to 85% by weight of a vinyl lactam, forexample, N-vinyl pyrrolidone. A variety of N-vinyl lactams are disclosedaccording to a structural formula presented within. The most preferredvinyl lactam is N-vinyl-2-pyrrolidone. U.S. Pat. No. 4,430,458, entitled“Hydrogel-Forming Polymeric Materials,” to Tighe, et al., issued Feb. 7,1984, discloses polymeric materials suitable for making contact lensesformed by copolymerization and crosslinking of an amide of anunsaturated carboxylic acid, an N-vinyl lactam, an ester of anunsaturated carboxylic acid, an unsaturated carboxylic acid, and apolymerizable hydrophobic vinyl monomer. This patent claims a contactlens in the form of a hydrogel comprising a crosslinked polymericmaterial containing units derived either by simultaneouscopolymerization and crosslinking or by co-polymerization and subsequentcrosslinking of the following monomers: 20 to 40 mole percent of anamide of acrylic of methacrylic acid; 25 to 55 mole percent of anN-vinyl lactam of the N-vinyl pyrrolidone type; 5 to 20 mole percent ofan hydroxy alkyl ester of acrylic or methacrylic acid; 1 to 10 molepercent of acrylic or methacrylic acid; and at least about 5 up to about10 mole percent of a polymerizable hydrophobic vinyl monomer. U.S. Pat.No. 4,022,754, entitled “Novel copolymer having utility as contactlens,” to Howes, et al., issued May 10, 1997, discloses a method toprepare terpolymers containing 3-methoxy-2-hydroxy-propyl methacrylate,N-vinylpyrrolidone, and methyl methacrylate, suitable for contact lens.

[0009] The use of an IPN hydrogel contact lens material has been foundmuch less common, for instance, consider the following patents. U.S.Pat. No. 4,536,554, entitled “Hydrophilic polymers and contact lensesmade therefrom,” to Lim, et al., issued Aug. 20, 1985, discloses thepreparation of soft contact lenses made from IPN obtained by thepolymerization of a mixture containing a hydrophilic vinylpyrrolidonemonomer and a hydrophobic acrylic ester monomer in the presence ofmultiple crosslinking agents. U.S. Pat. No. 5,674,942, entitled“Interpenetrating polymer networks for contact lens production,” toHill, et al., issued Oct. 7, 1997, discloses another IPN method usingpolyurea interlocked with polyacrylate; the former polymer is preparedfrom amines and isocyanates while the latter polymer is prepared fromacrylic esters using a free radical initiator.

[0010] The following patents also disclose hydrogels:

[0011] U.S. Pat. No. 4,990,582, entitled “Fluorine-Containing SoftContact Lens Hydrogels,” to Salamone, issued Feb. 5, 1991, discloses asoft contact lens material that exists as a hydrogel and is formed by apolymer containing a fluorinated monomer, a hydroxy alkyl ester ofacrylic or methacrylic acid, and an N-vinyl lactam, According to thedisclosure, an N-vinyl lactam is present from 5 to 80% by weight. Theaddition of the N-vinyl lactam is critical in combination with thefluoromonomer and the hydroxy alkyl ester of acrylic or methacrylicacid, to obtain clear bulk copolymers without any haze or opacity. Thepreferred N-vinyl lactam is N-vinyl pyrrolidone in concentrations from 5to 80% by weight and preferably from 40 to 60% by weight. In the claims,about 10 to about 50 parts by weight of N-vinyl lactam is present.

[0012] U.S. Pat. No. 4,829,126, entitled “High Water-Absorptive SoftContact Lens,” to Nakajima et al., issued May 9, 1989, discloses ahighly water-absorptive soft contact lens made of a copolymer comprising10 to 40 parts by weight of an acrylate or methacrylate polymer and 60to 90 parts by weight of a hydrophilic monomer. To achieve a balancebetween structural integrity and water absorption, methacrylate monomershaving a hydrophilic group are used, such as the N-vinyl lactam, N-vinylpyrrolidone.

[0013] U.S. Pat. No. 4,620,954, entitled “Hydrogel fromUltraviolet-Initiated Copolymerization,” to Singer, et al., issued Nov.4, 1986, discloses a contact lens hydrogel prepared by copolymerizing 70parts of N-vinyl pyrrolidone and 23 parts of phenyl ethyl methacrylate,together with allyl methacrylate as a crosslinker, T-butyl peroctoate asa thermal initiator and 2,2-dimethoxy-2-phenylacetophenone or benzoinmethyl ether as a photo initiator. The patent discloses N-vinylpyrrolidone as a preferred N-vinyl lactam monomer and phenylethylmethacrylate as a preferred hydrophobic acrylate.

[0014] U.S. Pat. No. 4,440,919, entitled “Low N-Vinyl Lactam ContentBased Biomedical Devices,” to Chromecek et al., issued Apr. 3, 1984,discloses N-vinyl lactam content copolymers that are crosslinked withresonance-free dye (alkine tertiary amine) cyclic compounds to obtainbiomedical devices such as soft contact lenses. This patent alsodiscloses the use of water-soluble diluents for use in theaforementioned polymer system to modify the physical properties of theseproperties. Such diluents are present, preferably, at not more than 30weight percent. Diluents include low molecular weight, e.g., 500 to10,000, linear poly (vinyl pyrrolidone).

[0015] U.S. Pat. No. 4,184,992, entitled “Cross-Linked AlkylMethacrylate-N-Vinyl Lactam Polymer Composition for Use in Soft ContactLenses,” to Hosaka, issued Jan. 22, 1980, discloses a crosslinkedpolymer composition prepared by polymerizing, using a bulkpolymerization procedure, a monomer mixture comprising an alkylmethacrylate and an N-vinyl lactam in the presence of a crosslinkingagent such as vinyl acrylate, vinyl methacrylate, triallyl isocyanurateand vinyl carboxylates. This patent discloses 2-hydroxyethylmethacrylate (“HEMA”)/N-vinyl pyrrolidone copolymer gels. Such gels areprepared by copolymerizing HEMA with N-vinyl pyrrolidone orgraft-copolymerizing HEMA onto poly-N-vinyl pyrrolidone. A main point ofthis particular patent resides in the crosslinking agent used incombination with the methacrylate/N-vinyl lactam copolymerized mixture.

[0016] U.S. Pat. No. 4,045,547, entitled “Fabrication of Soft ContactLens and Composition Therefor,” to Le Bouef et al., issued Aug. 30,1977, discloses a contact lens composition comprising from 67.2% to79.3% HEMA; from 14.25% to 35% PVP; from 0.1% to 4.04% EDMA; from 0.1%to 2.5% MA; from 0.1% to 5.0% water; from 0% to 4% PPMHQ inhibitor; andfrom 50 to 250 PPM MEHQ inhibitor.

SUMMARY OF THE INVENTION (DISCLOSURE OF THE INVENTION)

[0017] The present invention relates to hydrogels comprising aninterpenetrating polymer network (IPN). The IPN of the present inventioncomprise at least one polymer, formed through polymerization of monomer,and at least one interpenetrating polymer network agent. In preferredembodiments of the invention, the IPN agent comprises at least onepolymer selected from the group of polymers comprising one or moremonomeric units comprising at least one ═N—C(═O)— group having anaverage molecular weight of from approximately 500 to approximately300,000; polymers with one or more monomeric units comprising at leaston N-oxide group having an average molecular weight of fromapproximately 500 to approximately 300,000; polymers comprising both═N—C(═O)— and N-oxide groups of (A) and (B); and mixtures thereof. Toenhance properties of the hydrogels of the present invention, additionalmaterials are optionally added, such as, materials selected from thegroup consisting of monomers, polymer crosslinkers, polymerizationinitiators, ultraviolet absorbing material, colorant, antiseptic agents,and combinations thereof.

[0018] The IPN hydrogels of preferred embodiments of the presentinvention have a water loss of less than approximately 5 weight percentafter 5 minutes at approximately 75% humidity and approximately 24° C.Sample experiments demonstrating such water loss characteristics appearunder the Example section of this disclosure wherein details of theexperimental procedure also appear.

[0019] In preferred embodiments of the present invention, theaforementioned at least one polymer, formed through polymerization ofmonomer, comprises monomer selected from the group consisting of:2-hydroxyethylmethacrylate, 2-hydroxyethylacrylate, methylmethacrylate;methylacrylamide; methacrylamide; N,N-dimethyl-diacetoneacrylamide;2-phosphatoethylmethacrylate; di-, tri-, tetra-, penta-, . . .polyethyleneglycol monoacrylate and methacrylate; 4- and2-methyl-5-vinylpyridine; N-(3-methacrylamidopropyl) -N,N-dimethylamine;N-(3-methacrylamidopropyl) -N,N,N-trimethylamine; 1-vinyl-, and2-methyl-1-vinlyimidazole; N-(3-acrylamido-3-methylbutyl)-N,N-dimethylamine; N-methylacrylamide; 3-hydroxypropyl methacrylate;N-vinyl imidazole; N-vinyl succinimide; N-vinyl diglycolylimide; N-vinylglutarimide; N-vinyl-3-morpholinone; N-vinly-5-methyl-3-morpholinone;propyl methacrylate; propyla crylate; butyl methacrylate; butylacrylate; pentyl acrylate; pentyl methacrylate; dimethyl diphenylmethylvinyl siloxane; N-(1,1-dimethyl-3-oxobutyl)acrylamide;2-ethyl-2-(hydroxymethyl)-1,3-propanediol trimethacrylate;X-(dimethylvinylsilyl)-ω-[(dimethylvinyl-silyl)oxy]-dimethyl diphenylmethylvinyl siloxane; butyl(meth)acrylate; 2-hydroxybutyl methacrylate;vinyl acetate; pentyl methacrylate; vinyl propionate;3-hydroxy-2-naphthyl methacrylate; vinyl alcohol;N-(formylmethyl)acrylamide; 2-ethoxyethyl methacrylate;4-t-butyl-2-hydroxycyclohexyl methacrylate; 2-(methacryloyloxy)ethylvinyl carbonate;vinyl[3-[3,3,3-trimethyl-1,1-bis(trimethylsiloxy)disiloxany]propyl]carbonate;4,4′-(tetrapentacontmethylhepta-cosasiloxanylene)di-1-butanol;N-carboxy-β-alanine N-vinyl ester; 2-methacryloyloxyethylphosphorylcholine, and combinations thereof. Variations of thesemonomers, well-known in the art of monomer chemistry and physics, arewithin the scope of the present invention, especially those monomerscapable of forming an IPN with the IPN agents of the present invention,in particular, those monomers capable of forming an IPN with IPN agentsPVP, PEOX, and PVNO. However, the IPN agents are not limited to PVP,PEOX, and PVNO. In general, IPN agents are polymers with one or moremonomeric units comprising at least on ═N—C(═O)— group having an averagemolecular weight of from approximately 500 to approximately 300,000;polymers with one or more monomeric units comprising at least on N-oxidegroup having an average molecular weight of from approximately 500 toapproximately 300,000; polymers comprising both ═N—C(═O)— and N-oxidegroups; and mixtures thereof. Therefore, for instance, polymerscomprising N-vinyl pyrrolidone monomer wherein the pyrrolidone groupappears on a less than one to one basis with respect to a polymerbackbone subunit, e.g., vinyl, are within the scope of the presentinvention. The IPN hydrogel compositions of the present inventionpreferably comprise at least one IPN agent that is present fromapproximately 1% by dry weight to approximately 14% by dry weight andmore preferably from 5% by dry weight to approximately 10% by dryweight. Regarding the average molecular weight of the IPN agent PVP, thepreferred average molecular weight is greater than 10,000. Again,optional materials selected from the group consisting of monomers,polymer crosslinkers, polymerization initiators, ultraviolet absorbingmaterial, colorant, antiseptic agents, and combinations thereof allowfor modification of the general IPN hydrogel to meet specific needs andrequirements, particularly for IPN-based contact lenses.

[0020] Preferred embodiments of the hydrogel compositions of the presentinvention also comprise optional monomer such as at least one sulfoxidecontaining agent selected from the group consisting: sulfoxidecontaining methacrylates, sulfoxide containing acrylates, andcombinations thereof. Although present in all examples presented within,the presence of crosslinker is also optional and comprises at least onemember selected from the group consisting of monomer and polymer. Forpolymer crosslinker comprising a polymer, a molecular weight range fromapproximately 300 to approximately 1500 is preferred. In preferredembodiments of the present invention, the crosslinker is present fromapproximately 0.1% by dry weight to approximately 8% by dry weight andpreferably from 0.5% by dry weight and approximately 4% by dry weight ofthe hydrogel. Preferred crosslinkers are polyethylene glycoldimethacrylate and ethylene glycol dimethacrylate, which are usefulalone or in combination. For instance, polyethylene glycoldimethacrylate having a molecular weight of approximately 400 is mixablewith that having a molecular weight of approximately 1000. Furthermore,material of varying molecular weight is combinable with crosslinkermonomer(s).

[0021] In preferred embodiments, the hydrogel compositions of thepresent invention optionally include monomers other than the “principalmonomer,” such as, but not limited to, at least one monomer selectedfrom the group consisting of methyl methacrylate and N-vinyl lactams.For instance, the list of optional monomer includes the N-vinyl lactam,N-vinylpyrrolidone. The principal monomer is so called to define aparticular group of monomers—at least one of which is always present inthe inventive hydrogel. Whereas optional monomers, on the other hand,are just that, optional. No limitation is made as to “principal” andweight percentage or parts, thus, IPN agent or optional monomer canexceed the weight percentage or parts of the principal monomer.

[0022] Again, a primary object of the present invention, as applied tocontact lenses, is water rentention. Preferred embodiments of thepresent invention use at least one interpenetrating network agentcomprising an agent selected from the group consisting ofpolyvinylpyrrolidone, poly-2-ethyl-2-oxazoline, and poly(4-vinylpyridineN-oxide). In particular, preferred embodiments of the present inventionusing PVP and/or PEOX have shown water loss of less than 4%.Combinations of PVP, PEOX, and PVNO, are within the scope of the presentinvention and are theoretically expected to produce results similar tothe hydrogels presented in the examples contained within.

[0023] A primary object of the present invention is to provide abiocompatible IPN-based hydrogel.

[0024] A primary advantage of the present invention is formation ofIPN-based hydrogels having superior water retention.

[0025] Other objects, advantages and novel features, and further scopeof applicability of the present invention will be set forth in part inthe detailed description to follow, and in part will become apparent tothose skilled in the art upon examination of the following, or may belearned by practice of the invention. The objects and advantages of theinvention may be realized and attained by means of the instrumentalitiesand combinations particularly pointed out in the appended claims.

[0026] It is a further primary object of the present invention toprovide a hydrophilic hydrogel contact lens prepared by an IPN process,having a good mechanical strength and elongation, and showing a lowdegree of surface friction, a low dehydration rate, and minimalbiodeposition.

[0027] It is another object of the present invention to provide ahydrophilic hydrogel contact lens prepared using an unsaturated alkyl(meth)acrylate or its derivatives as the principle monomers, optionallya vinyl containing comonomer(s), crosslinking agents, initiators, andoptionally other additives to impart the resulting contact lens specificproperties, in the presence of a soluble, hydrophilic IPN agent duringpolymerization process for the low, medium, and high water contentlenses of all kinds and types of geometric designs including but notbeing limited to spherical, aspheric, and toric.

[0028] It is a further object of the present invention to provide ahydrophilic hydrogel contact lens polymerized by a radiation such as,but not limited to, E-beam, ultraviolet and/or thermal, and microwave.

[0029] Objects of the present invention are achieved through formationof hydrophilic hydrogel contact lens using, for instance, monomers suchas unsaturated alkyl (meth)acrylate or its derivatives, preferably2-hydroxyelhyl methacrylate (HEMA); optionally a vinyl containingcomonomer(s), preferably methacrylic acid (MM), N-vinylpyrrolidone(NVP), or polyethylene(400) glycol (PEG 400) monomethyl ethermonomethacrylate; crosslinking agents, preferably polyethylene glycoldimethacrylate in a molecular weight range from 400 to 1000; initiators,preferably 2,2′-azobisisobutyronitrile (AIBN),2-hydroxy-2-methyl-1-phnyl-1-propanone (DAROCUR® 1173, E. Merck,Darmstadt, Germany), and 1,1′-azodi(hexahydrobenzonitirile); andoptional additives, preferably 2-hydroxy-4-acrylyloxyethoxybenzophenoneas a UV blocking agent and copper phthalocyanine blue as a handlingcolorant; in the presence of an IPN agent, preferablypolyvinylpyrrolidone (PVP) or poly-2-ethyl-2-oxazoline (PEOX), whereinpolymerization of monomers occurs through E-beam, ultraviolet, and/orthermal curing processes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS (BEST MODES FOR CARRYING OUTTHE INVENTION)

[0030] The present invention relates to an IPN composition, especially ahydrophilic hydrogel composition for contact lenses. More particularly,the present invention relates to polymerization of a mixture of monomersand a synthesized non-ionic polymer as an IPN agent using a crosslinkingagent or a mixture of crosslinking agents. After polymerization, viairradiation such as ultraviolet and/or thermal processing, the producedcrosslinked polymer is hydrated to form a hydrogel having a low degreeof surface friction, superior water retention, and a high degree ofbiodeposit resistance.

[0031] The present invention also relates to the contact lenspreparation including the polymerization process, prehydrated dry lenspreparation, and corresponding hydration process.

[0032] In accordance with the present invention, the principle monomerswhich can be used include, but are not limited to:2-hydroxyethylmethacrylate (HEMA); 2-hydroxyethylacrylate (HEA);methylmethacrylate (MMA); methylacrylamide (MAA); methacrylamide;N,N-dimethyl-diacetoneacrylamide; 2-phosphatoethylmethacrylate; di-,tri-, tetra-, penta-, . . . polyethyleneglycol monoacrylate andmethacrylate; 4 and 2-methyl-5-vinylpyridine;N-(3-methacrylamidopropyl)-N,N-dimethylamine;N-(3-methacrylamidopropyl)-N,N,N-tri methylamine; 1-vinyl-, and2-methyl-1-vinlyimidazole;N-(3-acrylamido-3-methylbutyl)-N,N-dimethylamine; N-methylacrylamide;3-hydroxypropyl methacrylate; N-vinyl imidazole; N-vinyl succinimide;N-vinyl diglycolylimide; N-vinyl glutarimide; N-vinyl-3-morpholinone;N-vinly-5-methyl-3-morpholinone; propyl methacrylate; propyl acrylate;butyl methacrylate; butyl acrylate; pentyl acrylate; pentylmethacrylate; dimethyl diphenyl methylvinyl siloxane;N-(1,1-dimethyl-3-oxobutyl)acrylamide;2-ethyl-2-(hydroxy-methyl)-i,3-propanediol trimethacrylate;X-(dimethylvinylsilyl)-ω-[(dimethylvinyl-silyl)oxy]-dimethyl diphenylmethylvinyl siloxane; butyl(meth)acrylate; 2-hydroxybutyl methacrylate;vinyl acetate; pentyl methacrylate; vinyl propionate;3-hydroxy-2-naphthyl methacrylate; vinyl alcohol;N-(formylmethyl)acrylamide; 2-ethoxyethyl methacrylate;4-t-butyl-2-hydroxycyclohexyl methacrylate; 2-(methacryloyloxy)ethylvinyl carbonate;vinyl[3-[3,3,3-trimethyl-1,1-bis(trimethylsiloxy)disiloxany]propyl]carbonate;4,4′-(tetrapentacontmethylhepta-cosasiloxanylene)di-1-butanol;N-carboxy-β-alanine N-vinyl ester; 2-methacryloyloxyethylphosphorylcholine and the like.

[0033] Among these monomers, 2-hydroxyethylmethacrylate (HEMA) ispreferred and the HEMA chemical structure is shown in Structure 1.

[0034] The concentration of the principle monomer is typically in therange of 5% to 95% by weight, and preferably in the range of 20% to 85%,depending upon the desired properties of the resulting hydrogels.

[0035] If desired to prepare a hydrogel having a water content greaterthan 40%, eg., preparation of mid- or high water content contact lens,the use of additional highly hydrophilic comonomer is necessary. Theadditional highly hydrophilic comonomers useful in the present inventioninclude, but are not limited to, acrylic acid, methacrylic acid,sulfoxide containing (meth)acrylate, N-vinylpyrrolidone,2-acrylamido-2-methylpropanesulfonic acid and its salts, vinylsulfonicacid and its salts, styrenesulfonic acid and its salts,3-methacryloyloxy propyl sulfonic acid and its salts, allylsulfonicacid, 2-methacryloyloxyethyltrimethylammonium salts,N,N,N-trimethylammonium salts, diallyl-dimethylammonium salts,polyethylene glycol (400) monomethyl ether monomethacrylate, glycerolmonomethacrylate, and the like.

[0036] To obtain a greater water content non-ionic hydrogel, thepreferred additional comonomers are N-vinylpyrrolidone, sulfoxidecontaining (meth)acrylate, polyethylene glycol(400) monomethyl ethermonomethacrylate, and glycerol monomethacrylate whose chemicalstructures are illustrated in Structure 2 to 5, respectively.

[0037] Where n can be 1,2, and 3; R₁ can be either H or CH₃; and R₂ canbe either CH₃ or C₂H₅.

[0038] Polyethylene glycol (400) nionomethyl ether monomethacrylate

[0039] Where n is an integral indicating the number of repeating unitsfor a specific molecular weight. In the case of polyethylene glycol(400) monomethyl ether monomethacrylate, n is 7.

[0040] Sulfoxide containing methacrylates (SMA) and sulfoxide containingacrylate (SA) are a preferred constituent of the present invention. Theconcentration of SMA and/or SA is in the range of approximately 5% toapproximately 70% by weight, and preferably in the range ofapproximately 10% to approximately 50% by weight, depending on watercontent and other desired properties of the resulting hydrogels.

[0041] To obtain a greater water content ionic hydrogel, the preferredadditional comonomers in the present invention are methacrylic acid andacrylic acid whose general chemical structures are show in Structure 6.

[0042] Where R can be either H or CH₃

[0043] The concentration of additional comonomers in the presentinvention is typically in the range of 0% to 80% by weight, andpreferably in the range of 0% to 60%, depending upon the type ofcomonomer used, the water content, and other desired properties of theresulting hydrogel.

[0044] To form a hydrophilic hydrogel the use of crosslinker isrequired. Typically, the crosslinkers are di-functional ormultifunctional compounds that can incorporate themselves into theresulting polymer backbone during the polymerization process. Examplesof crosslinkers include, but are not limited to, ethyleneglycoldi(meth)acrylate, triethyleneglycol di(meth)acrylate, tetraethyleneglycol di(meth)acrylate, trimethylopropane tri(meth)acrylate, bisphenolA di(meth)acrylate, ethoxylate bisphenol A di(meth)acrylate,pentaerythritol tri-, and tetra(meth)acrylate, tetramethylenedi(meth)acrylate, methylenebisacrylamide, methacryloxyethyl vinylcarbonate, triallylcyanurate, methacryloxyethyl vinyl urea, divinylbenzene, diallyl itaconate, allyl methacrylate, diallyl phthalate,polysiloxanylbisalkyl (meth)acrylate, polyethylene glycoldi(meth)acrylate, and the like. The preferred crosslinker in the presentinvention is polyethylene glycol dimethacrylate having the molecularweight of approximately 400 or approximately 1000, as illustrated inStructure 7.

[0045] Where n is an integral indicating the number of repeating unitfor a specific molecular weight. In the case of molecular weight ofapproximately 400 and approximately 1000, n is 5 and 19, respectively.

[0046] The concentration of crosslinking agent is chosen according tothe required degree of crosslinking and consequently it is determinednot only by the amount of the crosslinker but by the type and ability toform the crosslinked polymer. The less effective crosslinking agentshave to be applied in a higher concentration than the more effectiveones, and while in general up to 8% by weight of the crosslinker ispossible, preferably, the more effective crosslinkers are present up to3% by weight.

[0047] The polymers of the present invention are preferentially preparedby radical polymerization utilizing the free radical initiators.Generally, E-beam, ultraviolet, microwave, and thermal process are usedto initiate the polymerization. Preferably, ultraviolet and/or thermalpolymerization are used alone or in combination. The thermal initiatorsare preferably either azo- or peroxide families, including but not beinglimited to, 2,2′-azobisisobutyronitrile (AIBN), 1,1′-azodi(hexahydrobenzonitrile), 2,2′-azobis (2,4-dimethylpentanenitrile),4,4′-azobis (4-cyanopentanoic acid), 2,2′-azobis(2-methylbutanenitrile),2,2′-azobis(2,4-dimethyl-4-methoxylvaleronitrile), t-butyl peroctoate,benzoyl peroxide, lauroyl peroxide, methyl ethyl ketone peroxide,2,4-olichlorobenzoyl peroxide, p-chlorobenzoyl peroxide, di-isopropylperoxycarbonate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy) hexane, andthe like. More preferably, the thermal initiators are AIBN and 1,1-azodi(hexahydroben-zonitrile) in the present invention. The photoinitiatorsuseful in the present invention include, but are not limited to,hydroxyalkylphenone such as 2-hydroxy-2-methyl-1-phenyl-1-propanono(DAROCUR® 1173), benzoin methyl ether (BME), and2,2-dimethoxy-2-phenylacetophenone.

[0048] The concentration of initiators used may be, for example, from0.01% to 5% by weight, and is preferably from 0.2% to 1% by weight. Ifthe quantity of initiators is too low, the resulting hydrogel may not besufficiently resilient to spring back quickly or completely afterfolding and if the quantity is too high, a stiff but less elasticresulting hydrogel may be formed.

[0049] To impart specific properties to the resulting hydrogel,additives are useful. For instance, an ultraviolet (UV) absorbingmaterial is added to reduce penetration of UV radiation in the hydrogelin the wavelength of 300 to 410 nm. Of particular interest are thebenzophenone and benzotriazole familes of UV absorbers, such as2,2′-dihydroxy-4-methacryloyloxybenzophenone,2,2′-dihydroxy-4,4′-dimethacryloyl′-oxybenzopherie,2-hydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy) benzophenone,2,2′-dihydroxy-4,4′-(3-bismethacrylo-yloxy-2-hydroxypropoxy)benzophenone, 1-, 4-, 5-, 6-, or 7-vinylbenzotriazole 4-, 5-, 6-, 7-,methacryloyloxybenzotriazole, 1-methacryloylbenzotriazole, 4-, 5-, 6-,or 7-methacryloyloxy-2-hydroxypropoxybenzotriazole,1-(methacryloyloxy-2-hydroxypropoxy) benzotriazole, and the like. Amongthese UV absorbing materials, 2-hydroxy-4-acrylyloxyethoxy benzophenoneis preferably used in the present invention in a concentration range of0.01% to 1%, and more preferably in a range of 0.1% to 0.4% by weight.

[0050] In addition, other additives such as handling colorant can alsobe employed in the hydrogel composition. Typical handling colorant iscopper phthalocyanine blue in the present invention in a very smallquantity that has been commonly used in the contact lens manufacture.

[0051] The polymers used in the present invention as IPN agents arethose that are homogeneously miscible with the monomer mixture atambient temperature. These IPN agents are typically water solublepolymers including polyvinylpyrrolidone (PVP) having a molecular weightof 10,000 to 100,000 and preferably in the range of 30,000 to 80,000, asillustrated in Structure 8; poly-2-ethyl-2-oxazoline (PEOX) having amolecular weight of 10,000 to 1,000,000; and preferably in the range of50,000 to 500,000, as shown in Structure 9; polyglycerol methacrylate asillustrated in Structure 10; and polyvinyl-pyrrolidone-iodine complex,as illustrated in Structure 11.

[0052] A prominent feature of the IPN agents of the present invention,is water solubility due to hydrophilic groups, such as ═N—C(═O)— groups.Examples of polymers containing ═N—C(═O)— groups include:polyvinylpyrrolidone (PVP); polyvinyloxazolidone;polyvinylmethyloxazolidone; polyacrylamide and N-substitutedpolyacrylamides, wherein R groups are independently selected from H andC1-C6 alkyl groups, e.g., methyl, ethyl, propyl, or isopropyl, or two Rgroups can form a 5 or 6 member ring structure; polymethacrylamide andN-substituted polymethacrylamides, wherein R groups are as describedabove; poly(N-acrylylglycinamide); poly(N-methacrylylglycinamide);poly(2-ethyl-2-oxazoline) (PEOX); and polyvinylurethane, wherein each Rgroup is as described above. These polymers have an amphiphiliccharacter with polar groups conferring hydrophilic properties and apolargroups conferring hydrophobic properties. Of course the strength of anyparticular polar group, and combinations thereof, are variablesconsidered within the scope of the present invention. Detaileddescription of physicochemical properties of some of these polymers aregiven in “Water-Soluble Synthetic Polymers: Properties and Behavior,”Vol. 1, Philip Molyneux, CRC Press, 1983. These polymers are also usefulin the present invention in partially hydrolyzed and/or crosslinkedforms.

[0053] PVP, also known as povidone, is available in molecular weightsranging from approximately 1,000 to approximately 1,000,000. Due to itswidespread use as a suspending or dispersing agent, in certainembodiments of the present invention, materials are suspended ordispersed in PVP to form a pre-mix. The same method of use applies tothe aforementioned ═N—C(═O)— group containing polymers.

[0054] PVP-lodine, also known as povidone-iodine (PVP-I₂), has knownanti-infective properties. The same method of use applies to theaforementioned ═N—C(═O)— group containing polymers wherein iodine ispresent. These particular polymers also have the potential for UVabsorption. Under such circumstances, the concentration of UV initiatoris adjustable to compensate for processes relying on UV initiatedpolymerization.

[0055] N-oxides of heterocyclic compounds such as the N-oxides ofpyridine, pyrrole, imidazole, pyrazole, pyrazine, pyrimidine,pyridazine, piperidine, pyrrolidone, azolidine, morpholine, andderivatives thereof are also useable alone or in combination with theaforementioned polymers. For example, poly(4-vinylpyridine N-oxide)(PVNO) is useable alone or in combination with PVP and/or PVP-I₂.

[0056] Structures of some of the aforementioned polymers follow:

[0057] Where n is an integral indicating the number of repeating unit ofmonomer for constructing the polymer.

[0058] Where n is an integral indicating the number of repeating unit ofmonomer for constructing the polymer.

[0059] Where n is an integral indicating the number of repeating unit ofmonomer for constructing the polymer.

[0060] Where n is an integral indicating the number of repeatingmonomeric units for a specific molecular weight.

[0061] The concentration of IPN agents used in the present invention istypically in the range of 1% to 14%, but preferably in the range of 5%to 10% depending upon the desired properties of the resulting hydrogels.It has been found that if a higher concentration is used, the resultinghydrogel generally has a higher water content but with a weakermechanical strength. Surprisingly, when polyvinylpyrrolidone (PVP) isused as an IPN agent in a concentration greater than 5%, the resultinghydrogel exhibits a noticeable low degree of surface friction differinggreatly from the surface friction characteristics of other hydrophilichydrogels comprising conventional monomers made through a non-IPNprocess. Furthermore, the hydrophilic hydrogels prepared by the IPNprocess using PVP as an IPN agent show markedly lower water loss that isattributable to dehydration when compared to non-IPN processedanalogues. This suggests that the IPN agents such as PVP present in thehydrophilic hydrogel have a higher degree of water attraction abilitythat in turn prevents water evaporation from the hydrogel surface. Inaddition, the IPN processed hydrogel shows a lower protein and a lowerlipid absorption rate than other non-IPN processed hydrogels when anartificial tear fluid is tested at 37° C. for 7 days.

[0062] Polymers according to the invention can be produced by a varietyof methods, such as bulk polymerization, solution polymerization, orpossibly suspension polymerization in non-aqueous solution. Preferablybulk polymerization is used in the present invention. It is possible topolymerize purely by a thermal process, a photochemical process, or bycombining both of these processes. It is also possible to performpolymerization using microwave or E-beam as the energy source. When acombination of polymerization by thermal process and photochemicalprocess is employed, it is preferable first to proceed using anultraviolet photochemical process followed by a thermal process. Duringthe thermal polymerization process, if desired, the polymerizationtemperature is maintained as a constant throughout the entire thermalprocess, or alternatively, increased in a stepwise or continuous manner.

[0063] The polymeric material obtained by polymerization of thepolymerizable compositions according to the present invention ismanufacturable by first dispensing the composition directly in a moldhaving a desired form and then by performing the polymerization of thepolymerizable composition in the mold. When the polymeric material is afinished resulting polymer, the surfaces of the mold should have thegeometry which is the counter part of the resulting polymer. However,when the polymeric material produced is not a finished material, theconventional machining operation such as lathing can be used to producethe material of the desired geometry.

[0064] It is also possible to produce a semi-finished polymericmaterial, exhibiting one of its surfaces whose geometry is defined, theother surface being the subject of a machine operation, for instancelathing, after it has been obtained in order to produce the finishedpolymeric material. To produce the semi-finished polymeric material, itis also possible to proceed either by static molding or optionally byperforming a rotary spin casting.

[0065] The hydrated polymeric materials, i.e., hydrophilic hydrogels, inthe present invention are obtainable by subjecting the finished polymerto hydration in deionized water, an aqueous salt solution, an aqueoussurfactant solution, an alcoholic aqueous solution at ambient orelevated temperature for a sufficient period of time to reach a fullyhydrated state, or combinations thereof.

[0066] The following examples illustrate the present invention ingreater detail, but are not intended to limit the scope thereof in anyway.

Water Content

[0067] The hydrated lens samples (10 pieces) were lightly blotted usingan optical cloth and immediately transferred to an analytical balance(±0.0001g in precision) and weighed. The lens samples were then placedin a thermal oven at 120° C. for 16 hours to dehydrate the lens samples,and finally weighed again on the same balance. The water content wascalculated according to the equation below.

Water Content(%)=(wet weight of lens−dry weight of lens)÷dry weight oflens

Light Transmittance

[0068] The light transmittance of lens samples in saline was measuredusing a Beckman DU-64 spectrophotometer scanning from 400 nm to 800 nmat a speed of 750 nm/minute. The light transmittance of lens wasexpressed in %.

Lens Dehydration Rate

[0069] This testing procedure was developed as an in vitro method tomeasure the amount of water loss from the hydrophilic hydrogen contactlens under controlled humidity and temperature (humidity was controlledat 75%±2% and temperature was controlled at 24° C.±1° C.). A givenhydrated lens sample was first placed in UNISOL® 4 preservative free, pHbalanced saline solution for 10 minutes for equilibration, then removedand gently blotted using an optical cloth to remove the surface water onthe lens sample for about 3 seconds. The lens sample was thenimmediately placed on an analytical balance with a precision of ±0.0001g and the initial weight was recorded and the value output through anautomatic printer. Subsequently, the weight of the lens sample wasrecorded periodically at 30 seconds intervals for a period of 5 minutes.The initial weight and the final weight (5 minutes) were used todetermine the percentage of water loss of the lens sample according tothe following equation.

Water Loss(%)=[(final weight of lens sample÷initial weight of lenssample)−1]÷% of Water Content of lens sample

[0070] Table I, below, lists absolute values of Water Loss, per theaforementioned equation, including a comparison of various lensesprepared in the examples that follow. The water loss data of each lenssample represents an average from at least 3 measured values. TABLE IWater Loss Lens Sample Major Components (%) Example 1 HEMA/sulfoxidecontaining 3.1 acrylate/PVP Example 2 HEMA/sulfoxide containing 3.0acrylate/PVP Example 6 HEMA/MAA 6.0 Example 7 HEMA/MAA/PVP 3.3 Example 8HEMA/MAA/PVP 3.1 Example 9 HEMA/MAA 8.4 ¹PROCLEAR ® Omafilcon 5.4²BENZ-G ® 5X Hioxifilcon 8.6 ³FOCUS ® Vifilcon 14.3 ³FOCUS DAILIES ®Neificon 11.0

[0071] 1. PROCLEAR® (Biocompatibles Ltd., Middlesex, England) lens isrecognized in the market as an index lens providing improved comfort forcontact lens wearers who experience discomfort or symptoms related todryness during wear.

[0072] 2. BENZ-G® 5X (Benz Research and Development Corp., Sarasota,Fla.)

[0073] 3. FOCUS® and DAILIES® (Ciba-Geigy Corp., New York, N.Y.)

Degree of Polymerization

[0074] After preparation, and removal from the mold, each dry lenssample was weighed using an analytical balance (±0.0001 g in precision).The weighed lens sample was hydrated, first in deionized water—repeated2 times with agitation for about 30 minutes each time, then in a 15%isopropanol aqueous solution for about 30 minutes, and finally, twotimes in an aqueous saline solution with agitation for about 30 minuteseach time. After hydration, each lens sample was gently blotted using anoptical cloth, placed in a thermal oven at 120° C. for 16 hours, andfinally weighed again. The degree of polymerization expressed in % wascalculated according to the equation below.

Degree of Polymerization(%)=(initial dry weight of lens−final dry weightof lens)÷initial dry weight of lens

Synthesis of Methyl 3-(Acrylovloxy) Propyl Sulfoxide

[0075] 250 g of 3-methylthio-1-propanol and 500 mL of triethylamine wasadded, with agitation, to a 5 L, 2-neck round-bottom flask containing2500 mL of 4 Å molecular sieve dried methylene chloride chilled in acooling bath at −1° C. A mixture of 304 g of acryloyl chloride with 250mL of 4 Å molecular sieve dried methylene chloride was transferred tothe flask dropwise using a peristaltic pump at a rate of approximately 1drop per 3 seconds. The reaction mixture was continuously agitated afterthe completion of acryloyl chloride addition for an additional 2 hours,and then warmed to room temperature. The reaction mixture was washedwith deionized water (4 times with 1 L), saturated sodium bicarbonatesolution (2 times with 100 mL), and again with deionized water (2 timeswith 1 L). After separation, the methylene chloride layer of the mixturewas directly used in the subsequent oxidation outlined below.

[0076] The methylene chloride solution containing crude3-methylthio-1-propyl acrylate was transferred to a 3 L, 2-neckround-bottomed flask in a cooling bath at -1° C. with agitation. To thisflask, 370 g of 3-chloroperoxybenzoic acid powder (76.5 wt % averageactivity) was slowly added in portions over a period of about 24 hourswhile the mixture temperature was strictly maintained below 0° C. Afterthe substantial completion of the reaction, the mixture was evaporatedusing a rotary evaporator to strip off the solvent at 40° C. The slurryresidue was then extracted with deionized water (4 times with 1 L) andfiltered. The extraction procedure was conducted at room temperaturewith vigorous agitation. The extractant collected was mixed and stirredwith 120 g of Bio-Rad anion exchange resin (OH form) for 6 hours, andfiltered. The filtrate was then evaporated under reduce pressure at 50°C. to obtain a light brownish-yellow crude methyl-3-acryloyloxy propylsulfoxide. The final purification of methyl 3-acryloyloxy propylsulfoxide was conducted using a vacuum distillation technique to obtaina colorless oil product.

Industrial Applicability

[0077] The invention is further illustrated by the followingnon-limiting examples.

EXAMPLE 1

[0078] 62.35 parts of 2-hydroxyethylmethacrylate (99.5% minimal purity),20 parts of methyl 3-(acryloyloxy) propyl sulfoxide, 1.25 parts ofpolyethylene glycol (400) dimethacrylate, 1 part of polyethylene glycol(1000) dimethacrylate, and 0.5 parts of methacrylic acid were thoroughlymixed using a magnetic stirring bar. To this homogeneous solution, 14parts of polyvinylpyrrolidone (PVP), having a molecular weight of about38,000, was slowly added with agitation. Upon completion of this basemix, 0.5 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanon (DAROCUR®1173), 0.15 parts of 1,1′-azodi(hexahydrobenzonitrile), along with 0.25parts of 2-hydroxy-4-acrylyloxyethoxy benzophenone were added indarkness with agitation.

[0079] The mixture was then filtered through a 1.0 μm polypropylenefilter to remove any undissolved particles, followed by a vacuumdegassing to remove oxygen and air bubbles present in the filteredmixture for 5 minutes at ambient temperature. The degassed solution wasthen dispensed to polypropylene female lens molds in an approximateamount of 30 μl to 60 μl for each mold. After dispensing, the femalemolds were capped slowly with corresponding polypropylene male lensmolds. The assembly was then subject to UV polymerization using a UVlight with an approximate energy level of 4 watts/inch for 4 to 5minutes with no nitrogen blanket. After UV polymerization, the assemblywas immediately transferred to a thermal oven for thermal curing at 105°C. for 1 hour followed by 170° C. for an additional hour. Uponcompletion of polymerization, the assembly was removed from the oven,and opened to separate the lens from the molds. The dry lens sample washydrated, first in deionized water—repeated 2 times with agitation forabout 30 minutes each time, then in a 15% isopropanol aqueous solutionfor about 30 minutes, and finally, two times in an aqueous salinesolution with agitation for about 30 minutes each time.

[0080] The hydrated lens so prepared shows a light transmittance greaterthan 98%, the degree of polymerization above 95% based on thegravimetric analysis of the dry lens and the re-dried hydrated lens,water content about 60%, and a low degree of surface friction that isespecially tactilely noticeable. HEMA (99.5%) 62.35 methyl3-(acryloyloxy) propyl sulfoxide 20 PEG 400 dimethacrylate 1.25 PEG 1000dimethacrylate 1 Methacrylic acid 0.5 PVP (approx. 38 K) 142-hydroxy-2-methyl-1-phenyl-1-propanon 0.51,1′-azodi(hexahydrobezonitrile) 0.15 2-hydroxy-4-acrylyloxyethoxybenzophenone 0.25 TOTAL 100

EXAMPLE 2

[0081] 62 parts of 2-hydroxyethylmethacrylate (99.5% minimal purity), 20parts of methyl 3-(acryloyloxy) propyl sulfoxide, 1.25 parts ofpolyethylene glycol (400) dimethacrylate, 1 part of polyethylene glycol(1000) dimethacrylate and 0.5 parts of methacrylic acid were mixedthoroughly. To this solution 14 parts of polyvinylpyrrolidone, having amolecular weight of about 38,000, was slowly added with vigorousagitation. After this, 0.5 parts of2-hydroxy-2-methyl-1-phenyl-1-propanone (DAROCUR® 1173), 0.5 parts2,2′-azobisisobutyzonitrile (AIBN), and 0.25 parts of2-hydroxy-4-acrylyloxyethoxy benzophenone were added to the solution indarkness with agitation.

[0082] The mixture was then filtered, degassed, dispensed in thepolypropylene molds, and UV polymerized in the same manner as describedin Example 1. After UV polymerization, the assembly was immediatelysubject to thermal curing at 105° C. for 1 hour, followed by 120° C. foran additional 4 hours.

[0083] Upon completion of polymerization, the dry lens hydrationprocedure was carried out in a similar manner as that described inExample 1 without any variation. The hydrated lens so prepared hassimilar properties to that prepared in Example 1.

EXAMPLE 2

[0084] HEMA (99.5%) 62 methyl 3-(acryloyloxy) propyl sulfoxide 20 PEG400 dimethacrylate 1.25 PEG 1000 dimethacrylate 1 Methacrylic acid 0.5PVP (approx. 38 K) 14 2-hydroxy-2-methyl-1-phenyl-1-propanon 0.52,2′-azobisisobutyzonitrile (AIBN) 0.5 2-hydroxy-4-acrylyloxyethoxybenzophenone 0.25 TOTAL 100

EXAMPLE 3

[0085] 59 parts of 2-hydroxyethylrnethacrylate (99.5% minimal purity),25 parts of N-vinylpyrrolidone, 1 part of polyethylene glycol (1000)dimethacrylate, 1 part of polyethylene glycol (400) dimethylacrylatewere mixed thoroughly to form a homogeneous solution. To this solutionwas added 14 parts to polyvinylpyrrolidone having a molecular weight ofabout 38,000 slowly with agitation. Upon completion of the base solutionpreparation, 0.1 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone(DAROCUR® 1173), 0.5 parts of 2,2′-azobisisobutyronitrile (AIBN), and0.25 parts of 2-hydroxy-4-acryloxyethoxybenzophenone were added to theabove solution with agitation at dark.

[0086] The solution was then filtered, degassed, dispensed, UV andthermally cured in the same manner as those described in Example 1except that the thermal curing process was conducted at 120° C. for 4hours. After polymerization, the dry lens hydration procedure wasperformed in a similar was as that described in Example 1.

EXAMPLE 3

[0087] HEMA (995%) 59 N-vinylpyrrolidone 25 PEG 400 dimethacrylate I PEG1000 dimethacrylate I PVP (approx. 38 K) 142-hydroxy-2-methyl-1-phenyl-1-propanon 0.1 2,2′-azobisisobutyzonitrile(AIBN) 0.5 2-hydroxy-4-acrylyloxyethoxy benzophenone 0.25 TOTAL 101

EXAMPLE 4

[0088] 86.8 part of 2-hydroxyethylmethacrylate (99.5% minimal purity),1.8 parts of methacrylic acid, and 0.4 parts of ethylene glycoldimethacrylate were thoroughly mixed at ambient temperature. To thissolution was added 10 parts of polyvinylpyrrolidone having a molecularweight of about 38,000 slowly with vigorous agitation. After this, 0.25parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone (DAROCUR® 1173), 0.5parts of 2,2′-azobisisobutyronitrile (AIBN), and 0.25 parts of2-hydroxy-4-acryloxyethoxy benzophenone were then added to the solutionat dark with agitation.

[0089] The solution was finally filtered, degassed, dispensed, cured,and hydrated in a way identical to those described in Example 3, exceptthat the thermal curing process was conducted at 120° C. for 2 hours.

EXAMPLE 4

[0090] HEMA (99.5%) 86.8 methacrylic acid 1.8 ethylene glycoldimethacrylate 0.4 PVP (approx. 38 K) 102-hydroxy-2-methyl-1-phenyl-1-propanon 0.25 2,2′-azobisisobutyzonitrile(AIBN) 0.5 2-hydroxy-4-acrylyloxyethoxy benzophenone 0.25 TOTAL 100

EXAMPLE 5

[0091] 62 part of 2-hydroxyethyl methacrylate (99.5% minimal purity),0.5 parts of methacrylic acid, 20 parts of N-vinylpyrrolidone, 1.25parts of polyethylene glycol (400) dimethacrylate, and 1 part ofpolyethylene glycol (1000) dimetlacrylate were mixed togetherthoroughly. To this solution was added 14 parts of polyvinylpyrrolidonehaving a molecular of 38,000 slowly with agitation. Then, 0.5 parts of2-hydroxy-2-methyl-1-phenyl-1-propanone (DAROCUR® 1173), 0.5 parts of2,2′-azobisisobutyronitrile (AIBN), and 0.25 parts of2-hydroxy-4-acryloxyethoxy benzophenone were added to the above solutionwith agitation at dark.

[0092] The solution was finally filtered, degassed, dispensed, cured,and hydrated in a similar way to those described in Example 3.

EXAMPLE 5

[0093] HEMA (99.5%) 62 methacrylic acid 0.5 N-vinyl pyrrolidone 20polyethylene glycol (400) dimethacrylate 1.25 polyethylene glycol (1000)dimethacrylate 1 PVP (approx. 38 K) 142-hydroxy-2-methyl-1-phenyl-1-propanon 0.5 2,2′-azobisisobutyzonitrile(AIBN) 0.5 2-hydroxy-4-acrylyloxyethoxy benzophenone 0.25 TOTAL 100

EXAMPLE 6

[0094] 98.15 parts of 2-hydroxyethyl methacrylate (99.5% minimalpurity), 0.5 parts of methacrylic acid, and 0.35 parts of ethyleneglycol dimethacrylate were mixed thoroughly using a magnetic stirrer. Tothis solution was added 0.5 parts of 2,2′-azobisisobutyronitrile (AIBN),0.25 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone (DAROCUR® 1173),and 0.25 parts of 2-hydorxy-4-acrylyloxyethoxy benzophenone withagitation at dark.

[0095] The solution was filtered, degassed, dispensed, polymerized, andlens hydration was then carried out in the similar manner to thosedescribed in Example 1, except that UV curing was conducted for 5 to 12minutes and the thermal curing was performed at 120° C. for 4 hours.

[0096] Example 6 HEMA (99.5%) 98.15 methacrylic acid 0.5 ethylene glycoldimethacrylate 0.35 2-hydroxy-2-methyl-1-phenyl-1-propanon 0.252,2′-azobisisobutyzonitrile (AIBN) 0.5 2-hydroxy-4-acrylyloxyethoxybenzophenone 0.25 TOTAL 100

EXAMPLE 7

[0097] The lens preparation was conducted in the same way as thatdescribed in Example 6, except that 10% of polyvinylpyrrolidone having amolecular weight of about 38,000 as an IPN agent was added to themonomer mix. HEMA (99.5%) 88.15 methacrylic acid 0.5 ethylene glycoldimethacrylate 0.35 PVP (approx. 38 K) 102-hydroxy-2-methyl-1-phenyl-1-propanon 0.25 2,2′-azobisisobutyzonitrile(AIBN) 0.5 2-hydroxy-4-acrylyloxyethoxy benzophenone 0.25 TOTAL 100

EXAMPLE 8

[0098] 86.86 parts of 2-hydroxyethyl methacrylate (99.5% minimalpurity), 2 parts of methacrylic acid, and 0.14 parts of ethylene glycoldimethacrylate were mixed together. Then, 10 parts ofpolyvinylpyrrolidone having a molecular weight of about 38,000 was addedto the above solution slowly with vigorous agitation. To this solution,0.5 parts of 2,2′-azobisisobutyronitrile (AIBN), 0.25 parts of2-hydroxy-2-methyl-1-phenyl-1-propanone (DAROCUR® 1173), 0.25 parts of2-hydroxy-4-acrylyloxyethoxy benzophenone with agitation at dark. Thelens was then prepared in the same manner as described in Example 6.

EXAMPLE 8

[0099] HEMA (99.5%) 86.86 methacrylic acid 2 ethylene glycoldimethacrylate 0.14 PVP (approx. 38 K) 102-hydroxy-2-methyl-1-phenyl-1-propanon 0.25 2,2′-azobisisobutyzonitrile(AIBN) 0.5 2-hydroxy-4-acrylyloxyethoxy benzophenone 0.25 TOTAL 100

EXAMPLE 9

[0100] 96.36 parts of 2-hydroxyethyl methacrylate (99.5% minimalpurity), 2.04 parts of methacrylic acid, and 0.6 parts of ethyleneglycol dimethacrylate were thoroughly mixed. To this solution were added0.5 parts of 2,2′-azobisisobutyronitrile (AIBN), and 0.5 parts ofbenzoin methyl ether (BME) with agitation at dark.

[0101] The monomer mix was filtered, degassed, dispensed in apolypropylene mold having semi-spherical shape, and cured under a UVlight with an approximate energy of 17 watts/inch² for 7 minutes with anitrogen blanket for 6 minutes, followed by a thermal post curing at 70°C. for 7 to 9 hours. The semi-finished lens blank was finally lathed andhydrated in a manner similar to that described in Example 1.

EXAMPLE 9

[0102] HEMA (99.5%) 96.36 methacrylic acid 2.04 ethylene glycoldimethacrylate 0.6 2,2′-azobisisobutyzonitriie (AIBN) 0.5 benzoin methylether (BME) 0.5 TOTAL 100

[0103] The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants, and/oroperating conditions of this invention for those used in the precedingexamples.

[0104] Although the invention has been described in detail withparticular reference to these preferred embodiments, other embodimentscan achieve the same results. Variations and modifications of thepresent invention will be obvious to those skilled in the art and it isintended to cover in the appended claims all such modifications andequivalents. The entire disclosures of all references, applications,patents, and publications cited above are hereby incorporated byreference.

What is claimed is:
 1. A hydrogel composition comprising: I. at leastone polymer; and II. at least one interpenetrating polymer networkagent, interpenetrating said at least one polymer, selected from thegroup consisting of: (A) at least one polymer comprising one or moremonomeric units comprising at least one ═N—C(═O)— group; (B) at leastone polymer comprising one or more monomeric units comprising at leaston N-oxide group; (C) at least one polymer comprising both ═N—C(═O)— andN-oxide groups of (A) and (B); and (D) mixtures thereof; III. at leastone polymer crosslinker selected from the group consisting ofpolyethylene glycol dimethacrylate and ethylene glycol dimethacrylate;and IV. optionally, at least one material selected from the groupconsisting of monomers, polymerization initiators, ultraviolet absorbingmaterials, colorants, antiseptic agents, and combinations thereof.
 2. Ahydrogel composition comprising: I. at least one polymer; and II. atleast one interpenetrating polymer network agent, interpenetrating saidat least one polymer, selected from the group consisting of: (A) atleast one polymer comprising one or more monomeric units comprising atleast one ═N—C(═O)— group; (B) at least one polymer comprising one ormore monomeric units comprising at least on N-oxide group; (C) at leastone polymer comprising both ═N—C(═O)— and N-oxide groups of (A) and (B);and (D) mixtures thereof; III. at least one sulfoxide containingmaterial selected from the group consisting of sulfoxide-containingmethacrylates, sulfoxide containing acrylates, and combinations thereof;and IV. optionally, at least one material selected from the groupconsisting of monomers, polymer crosslinkers, polymerization initiators,ultraviolet absorbing materials, colorants, antiseptic agents, andcombinations thereof.
 3. A interpenetrating polymer network, contactlens composition comprising: I. at least one polymer; and II. at leastone interpenetrating polymer network agent, interpenetrating said atleast one polymer, selected from the group consisting of: (A) at leastone polymer comprising one or more monomeric units comprising at leastone ═N—C(═O)— group; (B) at least one polymer comprising one or moremonomeric units comprising at least on N-oxide group; (C) at least onepolymer comprising both ═N—C(═O)— and N-oxide groups of (A) and (B); and(D) mixtures thereof; and III. optionally, at least one materialselected from the group consisting of monomers, polymer crosslinkers,polymerization initiators, ultraviolet absorbing materials, colorants,antiseptic agents, and combinations thereof.
 4. The composition of claim1 , 2 , or 3 wherein said at least one polymer comprises at least onepolymer comprising at least one monomer selected from the groupconsisting of: 2-hydroxyethylmethacrylate, 2-hydroxyethylacrylate,methylmethacrylate; methylacrylamide; methacrylamide;N,N-dimethyl-diacetoneacrylamide; 2-phosphatoethylmethacrylate; di-,tri-, tetra-, penta-, . . . polyethyleneglycol monoacrylate andmethacrylate; 4- and 2-methyl-5-vinylpyridine;N-(3-methacrylamidopropyl)-N,N-dimethylamine; N-(3-methacrylamidopropyl)-N, N, N-trimethylarnine; 1-vinyl-, and 2-methyl-1-vinlyimidazole;N-(3-acrylamido-3-methylbutyl)-N,N-dimethylamine; 3,-hydroxypropylmethacrylate; N-vinyl imidazole; N-vinyl succinimide; N-vinyldiglycolylimide; N-vinyl glularimide; N-vinyl-3-morpholinorie;N-vinly-5-methyl-3-morpholinone; propyl methacrylate; propyla crylate;butyl acrylate; pentyl acrylate; dimethyl diphenyl methylvinyl siloxane;N-(1,1-dimethyl-3-oxobutyl)acrylamide;2-ethyl-2-(hydroxy-methyl)-1,3-propanediol trimethacrylate;X-(dimethylvinylsilyi)-ω-[(dimethylvinyl-silyl)oxy]-dimethyl diphenylmethylvinyl siloxane; butyl(meth)acrylate; 2-hydroxybutyl methacrylate;vinyl acetate; pentyl methacrylate; vinyl propionate;3-hydroxy-2-naphthyl methacrylate; vinyl alcohol;N-(formylmethyl)acrylamide; 2-ethoxyethyl methacrylate;4-t-butyl-2-hydroxycyclohexyl methacrylate; 2-(methacryloyloxy)ethylvinyl carbonate; vinyl[3-[3,3,3-trimethyl- 1,1-bis(trimethylsiloxy)disiloxany]propyl] carbonate;4,4′-(tetrapentacontmethylhepta-cosasiloxanylene)di-1-butanol;N-carboxy-β-alanine N-vinyl ester; 2-melhacryloyloxyethylphosphorylcholine; and combinations thereof.
 5. The composition of claim1 , 2 , or 3 wherein said at least one interpenetrating polymer networkagent comprises from approximately 1% by dry weight to approximately 14%by dry weight and preferably from approximately 5% by dry weight toapproximately 10% by dry weight of said composition.
 6. The compositionof claim 2 or 3 further comprising at least one sulfoxide containingmaterial selected from the group consisting of sulfoxide-containingmethacrylates, sulfoxide containing acrylates, and combinations thereof.7. The composition of claim 1 , 2 , or 3 wherein said at least oneinterpenetrating polymer network agent comprises a weight averagemolecular weight greater than approximately 10,000.
 8. The compositionof claim 2 or 3 wherein said polymer crosslinker comprises at least onemember selected from the group consisting of at least one monomer and atleast one polymer.
 9. The composition of claim 6 wherein said at leastone polymer crosslinker comprises a polymer comprising a weight averagemolecular weight range from approximately 300 to approximately
 1500. 10.The composition of claim 6 wherein said at least one polymer crosslinkercomprises from approximately 0.1% by dry weight to approximately 8% bydry weight and preferably from approximately 0.5% by dry weight toapproximately 4% by dry weight of said composition.
 11. The compositionof claim 6 wherein said polymer crosslinker comprises at least onemember selected from the group consisting of polyethylene glycoldimethacrylate and ethylene glycol dimethacrylate.
 12. The compositionof claim 1 , 2 , or 3 wherein said optional monomers comprise at leastone monomer selected from the group consisting of methyl methacrylateand N-vinyl lactams.
 13. The composition of claim 11 wherein saidN-vinyl lactam comprises N-vinylpyrrolidone.
 14. The composition ofclaim 1 , 2 , or 3 wherein said interpenetrating network agent comprisesat least one agent selected from the group consisting ofpolyvinylpyrrolidone, polyvinylpyrrolidone iodine,poly-2-ethyl-2-oxazoline and poly(vinylpyridine N-oxide).
 15. Aninterpenetrating polymer network comprising at least one polymer and atleast one interpenetrating polymer network agent interpenetrating saidat least one polymer, said interpenetrating polymer network having awater loss of less than approximately 5.0 weight percent after 5 minutesat approximately 75% humidity and approximately 24° C. whereinpreferably said at least one polymer comprises at least one memberselected from the group consisting of HEMA and MAA, and preferably saidagent comprises at least one member selected from the group consistingof polyvinylpyrrolidone, polyvinylpyrrolidone iodine,poly-2-ethyl-2-oxazoline, and poly(vinylpyridine N-oxide).
 16. Aninterpenetrating polymer network composition comprising sulfoxide.